Document and Entity Information	6 Months Ended
	Jun. 30, 2012	Jul. 31, 2012
Document And Entity Information [Abstract]
Entity Registrant Name	OM GROUP INC
Entity Central Index Key	0000899723
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Jun. 30, 2012
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	Q2
Amendment Flag	true
Entity Common Stock, Shares Outstanding		32,371,519
Amendment Description	Misclassification between SG&A and Cost of Goods Sold